Therefore, we move more slowly with age

The older we get, the slower we move. This applies whether we are going for a walk or just reaching for the remote control. A new study looks at why.

– The findings are exciting, because they can contribute to an increased understanding of why older people move more slowly than younger people, says Marius Myrstad, specialist in geriatrics, senior physician and researcher at Bærum Hospital, to NTB.

He has looked at the study from the United States, where a group of engineers at the University of Colorado Boulder believe they have demonstrated that the elderly need more energy than younger adults to perform the same physical tasks. The fact that older people move more slowly can therefore be partly due to the fact that it costs them more energy. Making movements slower is the body’s sensible way of meeting the challenge: Using less energy. The study is published in The Journal of Neuroscience.

– The researchers investigated two possible causal factors and found that both of these could be contributing to slower movement patterns. One of the most interesting findings was that older people, to about the same extent as younger people, were able to move faster when the movement triggered positive feedback – “reward”. This shows that the elderly retain the ability to learn, says Myrstad.

Healthy, fresh, but tougher

In the study, 84 subjects were divided into two groups: Young people aged 18 to 35 years and older people from 66 to 87 years. All participants were healthy and physically active at least three times a week. Both groups were given the same apparently simple task: to find and highlight a target on a screen. They were not told what the purpose of the study was. The elderly generally spent longer.

By analyzing the patterns of how they moved towards the target on the screen, the researchers discovered that the elderly appeared to change their movements along the way, as if to conserve energy.

– Whether we are young or old, we all have it in us, we are driven to get the most possible reward out of our surroundings, while at the same time minimizing the effort, says co-author Erik Summerside, who has a doctorate in mechanical engineering.

One hypothesis from the researchers is that older muscles work less efficiently, which means they have to burn more calories to carry out the same tasks as younger adults. It therefore requires more energy for an elderly person to walk with spring in their step or something as simple as getting up and getting something from the fridge.

Motivational reward

Another element the researchers point out is that aging changes the reward circuit in the brain. An older brain produces less dopamine, a neurotransmitter that gives you a sense of satisfaction after doing a good job. If you don’t get that good feeling by making a physical effort, it may be less likely that you can bear to stand a little extra. Dopamine production also decreases faster in people with Parkinson’s, for example, than is usual.

In part two of the study, participants received a reward when they succeeded in marking the target on the screen. Not a big one, but big enough to make the brain a little happy: the target on the screen exploded, they got points for the job, and it made a bing-bing sound. Overall, it served as a visual and audible pat on the back.

Both the younger and the older adults sharpened their skills and became 4–5 percent quicker to reach the goal when they realized that it would produce a bing-bing sound and points. But the way they improved was different. The young adults improved by generally making the whole movement faster. The elderly, on the other hand, concentrated better and were quicker to reach the goal by reducing their reaction time. A smarter way to reach the goal, according to the researchers, who believe the brain appears to be able to detect very small changes in how much energy the body uses and adjust its movements accordingly.

When the young adults added four kilograms of extra weight to the robot arm, and it became harder to make the movement quickly, their brains also did the same as the older ones: made the movement slower to use less energy, but sharpened the reaction time.

The ability to learn

The researchers believe that understanding the brain’s reward centers and prioritizing energy use can make it possible to find treatments that can reduce the burden of aging and disease. The aim is that the findings should contribute to developing better diagnostic tools for a number of disorders, including Parkinson’s, multiple sclerosis, depression and schizophrenia.

Myrstad says that this type of experiment can provide valuable knowledge, but that the mechanisms behind slower movement patterns in the elderly are probably far more complex than the findings in this study suggest.

– At the same time, it is extremely important and good that more research is done on this. These subjects were healthy, but also in patients with various diseases, precisely the ability to learn and train are important principles for rehabilitation. Rehabilitation is a very important part of the treatment for many diseases that affect the elderly, such as stroke, he says.

And for those who follow them up, it might be good to note the importance of giving positive feedback along the way.